Generally, a two-dimensional organic LED array for image manifestation apparatus applications is composed of a plurality of organic LEDs (one or more of which form a pixel) arranged in rows and columns. Each individual organic LED in the array is generally constructed with a light transmissive first electrode, an organic electroluminescent medium deposited on the first electrode, and a metallic electrode on top of the organic electroluminescent medium. The electrodes of the LEDs are connected to form a two-dimensional X-Y addressing pattern. In practice, the X-Y addressing pattern is achieved by patterning the light transmissive electrodes in an X direction and patterning the metallic electrodes in a Y direction (or vice versa if desired), with the X and Y directions being perpendicular to each other. The patterning of the electrodes is usually accomplished by either shadow mask or etching techniques. Due to the technical limits of shadow masks, etching processes are generally being utilized for high density information displays, which have pixel pitches less then 0.3 mm.
Organic electroluminescent display (OED) devices formed in the above manner, and especially organic light emitting devices (LEDs) and the like, generally are composed of three layers of organic molecules sandwiched between transparent, conductive and/or metallic conductive electrodes. The three layers include an electron transporting layer, an emissive layer, and a hole transporting layer. Charge carriers specifically, electrons and holes, generated in the electron and hole transporting region, recombine in the emissive layer to give off light. OED devices are attractive due to low weight, thin profile, and low driving voltage, i.e., less than about 20 volts. Hence, they have a potential application in many display devices.
While OED devices may find many applications in consumer and industrial products, a problem remains in the fact that they are not easily fabricated in a manner allowing for consistent device reliability and appropriate yield. In the prior art, it has been suggested to utilize integrated shadow masking to fabricate a pixelated organic electroluminescent display. The integrated shadow masks are generally built on top of the patterned transparent anode with a specific slop profile to avoid the need for angle evaporation. However, there exist a problem in manufacturing reliability, specifically consistency in the manufacturing line with regard to the specific slope profiles of the shadow masks. In addition, there has been shown to be an increase in the cross-talk associated with the device leakage between the anode and the cathode in a pixelated organic electroluminescent display with the integrated shadow mask. The leakage is mainly caused by the poor surface coverage of organic electroluminescent medium at the edge between the shadow mask and anode.
At the present time there exist a need to devise a relatively inexpensive and convenient organic electroluminescent display device, and method of fabrication that provides for increased reliability and consistency in the manufacturing line, as well as reliability in the device, specifically the avoidance of shorting or cross-talk between the integrated electrodes.
Accordingly, it would be highly advantageous to provide a new organic electroluminescent display device, and method of manufacturing which overcomes these problems.
It is a purpose of the present invention to provide for a new and improved organic electroluminescent display device and method of fabrication that is amenable to consistent commercial manufacturing line technology.
It is another purpose of the present invention to provide for a new and improved organic electroluminescent display device and method of fabrication that provides for high throughput, high reliability, and low manufacturing costs.